Gender Gap

I'd like to write about what we discussed in the last Sunday English club before I forget. The topic on that day was gender gap.

Firstly we have to know what gender is. Oxford Dictionary says "the fact of being male or female". I think this definition is not enough. The word gender is sometimes used in contrast to biological sex, so I'd like to add the difference in a social context to emphasise social and cultural dimention.

We talked about chores at work, women-only train car, timing of promotion and marriage for women, and so forth. After all, one guy said like this: there is a fact of gender gap, but the important thing is how we feel about it. If you feel uncomfortable, you should take action. If you don't feel anything, there's no gap for you actually. Gender gap is a matter which differs much depending on the cultural contidion.

I understand the concept, but I want to know where that difference comes from. According to the report "Women's Empowerment: Measuring the Global Gender Gap" in 2005 by World Economic Forum, the top country with the smallest gender gap is Sweden, while Japan is 38th in 58 countries.
http://www.weforum.org/en/initiatives/gcp/Gender%20Gap/index.htm
It seems that Sweden takes affirmative actions in many fields, not only in politics but also in any other time of employment and promotion. I'd like to know how Sweden forms those kind of social system.